(1) Field of the Invention
The present invention relates to a workpiece holding device, system and method.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98.
For processing, and particularly for machining workpieces, it is generally necessary to hold the workpiece in a fixed position and orientation. Generally, the workpiece is held using one or several devices such as clamps or vices, so as to prevent such movement of the workpiece during a processing step that could disturb the final shape or appearance of the workpiece after the process.
A particularly flexible type of workpiece holding device is represented by ball-and-socket workpiece holding devices, such as have been disclosed, for instance, in British patent GB 1,014,809 or European patent application EP 0 461 994 A1. Such workpiece holding devices of the state of the art comprise a substantially spherical ball with means for releasably retaining a workpiece, a socket with a first ball-receiving surface and means for mounting said socket on a worktable, and means for releasably clamping said ball against said first ball-receiving surface, so as to block rotational movement of said ball within said socket.
Before clamping the ball against the ball-receiving surface of the socket, the ball can rotate at least to a certain extent within the socket, thus allowing a user to orient the connecting means and the workpiece connected to it, so as to facilitate the work on said workpiece.
However, while they may provide three rotational degrees of freedom, the ball-and-socket workpiece holding devices of the state of the art do not provide any means for translationally adjusting the position of the ball, to adapt it, for instance, to workpieces with attachment points whose position may vary within certain manufacturing tolerances. While it has been proposed, for instance in EP 0 507 033 A1, to make the sockets themselves translationally moveable, the need for maintaining the position of the socket stable while the workpiece is processed results in mechanically complicated socket translation and locking devices.
While a ball-and-socket keyboard holding apparatus was proposed in U.S. Pat. No. 5,466,078 in which a ball-receiving element is mounted moveable within the socket along one axis in a plane perpendicular to the ball clamping force, the clamping means in this prior art is not suitable for reliably blocking the rotational movement of the ball within the socket against strong stresses, as generated, for instance, while machining a workpiece, and the apparatus has a separate lock tab for locking the ball-receiving element with respect to the socket. A first objective of the present invention is thus that of allowing at least limited translational adjustments to the position of the ball, while blocking such adjustments, at the same time as the rotational adjustments, by clamping the ball.